Conventionally, a condenser which condenses steam containing a noncondensable gas and exhausts the noncondensable gas is known (for example, see Japanese Patent Application Publication No. 4-244589). The condenser is formed with an exhaust port and the noncondensable gas such as air is exhausted to an air cooling unit through the exhaust port. The air cooling unit is provided with an air cooling unit pipe group, and the noncondensable gas exhausted to the air cooling unit is exhausted to an outside while non-condensed steam is condensed by the air cooling unit pipe group.